In Intellij IDEA I am selecting update tomcat application and then redeploy . It takes long time , why?

I am using Intellij IDEA, and in setting of tomcat I have select make project. I click Update tomcat application button in Debug window, then select redeploy. for the first and second redeploy it takes short time but after third or forth redeploy it takes long time . some times it take 20 minute. why? what do i have done that result this? I am using Intellij IDEA 14, and tomcat 8